You are here

The Radiation Mechanism of Fast Radio Bursts

Fast radio bursts (FRBs) are bright millisecond-duration transient events, first detected at ~GHz frequencies by the Parkes Telescope. There are about ten thousand bright (> 1 Jy ms) FRBs per day coming from random directions across the entire sky. One source discovered by the Arecibo Telescope, FRB 121102, was found to generate numerous bursts. This allowed follow-up observations to pin-point its host galaxy, which is at a distance of ~1 Gpc. The high brightness temperatures (> 1e35 K) of FRBs mean that the emission process must be coherent. We use the observed properties of the repeater FRB 121102 to constrain the plasma conditions for a wide variety of coherent emission processes. We find that none of the maser mechanisms in the literature can explain the high luminosity of FRBs without invoking unrealistic or fine-tuned plasma conditions. The most favorable mechanism is curvature emission by charge bunches near the surface of a magnetar (B > 1e14 G). We also show that propagation effects through the magnetosphere can explain the nearly 100% linear polarization and small variation of polarization angles for multiple bursts from FRB 121102, provided that the underlying neutron star has rotation period longer than about 0.3 second and its magnetic inclination is less than about 20 degrees.